The holders were given little hope of repeating their 1-0 final win over City in May, masterminded by now Everton boss Martinez and sealed with a Watson header in stoppage time which gave them their first major trophy.

But the Championship (second tier) club were not overawed by the task and produced a majestic, fearless display to dispel the doubters with Jordi Gomez's 27th penalty giving them a shock lead before James Perch doubled the advantage minutes into the second half.

Sami Nasri cut the lead with 20 minutes left but Wigan, relegated from the Premier League despite their cup exploits last term, somehow held firm against a barrage of attacks from the home side to set up a last four meeting with Arsenal.

"Drained. Happy," former City striker Rosler told reporters of his feelings after the final whistle.

"I am very happy for my players and staff and for Ben Watson, because he was a big incentive for us to do well for him."

Watson, who missed most of last season through injury before returning to net the Wembley winner against City in May, missed Sunday's memorable away success after suffering a double leg break in last month's league win at Barnsley.

Also proving an outside aide was popular former coach Martinez, whose Everton side were knocked out of the cup on Saturday by Arsenal.

"Last season was an unbelievable achievement from Roberto and his men to win the FA Cup and put Wigan on the map worldwide," said Rosler, who left third tier Brentford to replace Owen Coyle at Wigan in December.

"But to follow that up and reach the semi-final of the FA Cup is equally strong."

Rosler, who has helped steer the club back into promotion contention, said he had watched and learnt from Wigan's loss to City in the Premier League in April, less than a month before the FA Cup final success.

"I studied Roberto's tactics. He put out a very brave gameplan. I saw the league game where City won in the last five minutes 1-0 and Roberto's team played periods to perfection.

"We tried to replicate part of it but bringing our own identity, pressing and counter-attacking.

"I felt in the first half we surprised Manchester City because a lot of teams show Manchester City respect deservedly. Our only chance was to keep the ball in tight areas."

The visitors, though, struggled to keep the ball in the closing stages and their fine work looked to have been undone in the 84th minute when City substitute James Milner squared the ball for Edin Dzeko to knock into an empty net.

But somehow, Wigan defender Emmerson Boyce angled a long leg in front of the City striker and deflected the shot from five metres over the crossbar as the visitors hung on against the odds.

"That tackle was a match-winning, decisive moment for us," Rosler said. "That has shown the desire and willpower we have shown today.

"I can only take my hat off. Emmerson is a symbol of that, not only today, but since I worked in the club." (Writing by Patrick Johnston; editing by Amlan Chakraborty)